The present invention is directed to a reclosable plastic bag having an extruded fastener and to a method for forming such reclosable bag.
Reclosable plastic bags having extruded fasteners are well known in the art. Frequently the pouch portion is manufactured in one manufacturing operation and the extruded fasteners, manufactured in a different manufacturing operation, are adhered or heat sealed in an area adjacent an opening defined by the edge of the pouch. See for example U.S. Pat. Nos. RE 28,969; 3,633,642; 4,430,070; 4,601,694; 4,673,373; 4,736,451 and 5,017,021. Some of these patents, such as U.S. Pat. No. 3,633,642 provide a design in which the interlocking closure mechanism require the same amount of force to disengage the mechanism from the outboard side as from the inboard side. Others, such as U.S. Pat. Nos. 3,347,298; 3,425,469; 4,430,070; and RE 28,969 provide designs which require less force to open when having their outer peripheral edges pulled by a consumer than is required by opening from the inside, for example, from pressure exerted within the closed bag.
Some designs of extruded fastener elements are provided with a flange of greater thickness than the film material of the pouch which extend outwardly from the hook and groove toward the open end of the pouch to provide greater strength to the bag for opening than would be provided simply by the mouth-opening marginal portions of the pouch formed from the film material.
One method of affixing the extruded fasteners to the pouches utilizes a heat sealing operation for welding the extruded fastener members to the thinner film material. In other instances, adhesive is utilized to effect such connection.
In those instances in which the extruded fasteners are provided with flanges, it has been necessary, in heat sealing or welding the flange areas to the film material of the pouch, to utilize a complicated process to prevent the opposing flanges of the cooperating fastener members from becoming inadvertently welded together. Thus, it is efficient to effect the heat sealing of the fastener members to their respective sides of the pouch forming the mouth-opening by simultaneously passing between heated members both of the extruded fastener members, with each fastener member in interfacial engagement with the film at the respective edges of the pouch adjacent the open ends. The fastener members have substantially flat base surfaces opposite the hook and groove profile. The heated elements cause the film to become heat sealed to the flat base surface of each of the respective extruded fastener members. Although those portions of the- extruded fastener members forming the hooks and grooves have sufficient mass to prevent the hooks from becoming welded in the grooves of the opposing fastener member during heat sealing of the film to the base surfaces, the flanges, although substantially thicker than the film, have substantially less mass than the hook and groove portions of the extruded fasteners. As a result, problems can be encountered with the flanges of the opposing fasteners becoming welded together, thereby rendering the bag being formed unusable.
According to the present invention, the flange of at least one of the extruded fastener members is provided with one or more outwardly extending standoffs, each of which has an end portion in contact with the opposing flange of the opposing fastener member during the welding operation. The standoff elements provide an air gap between major portions of the opposing flanges and serve to prevent inadvertent welding of the opposing flanges together during the step of heat sealing the extruded fastener members to the respective walls of the bag adjacent the mouth opening. The standoff elements are extruded with the other portions of its extruded fastener forming with such other portions a unitary fastener.
Accordingly, it is an object of the present invention to provide a new bag design including an extruded fastener member which may be easily and efficiently assembled.
It is further an object of the present invention to provide a method for assembling a bag and extruded fastener member using a heat sealing process.
Other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description of the invention.